Heating systems and methods

ABSTRACT

A heating system comprising: a liquid supply system; a cell configured to: receive liquid from the liquid supply system, provide heating thereof, and output heated fluid; a work extraction system configured to extract useable work from heated fluid output from the cell; wherein the cell comprises: (i) a housing arranged to define an internal portion for receiving liquid to be heated, and (ii) a plurality of electrodes configured to apply electrical energy to fluid in the internal portion; and wherein the electrodes are configured to apply electrical energy to said fluid in the internal portion to generate one or more bubbles of plasma for releasing energy into said fluid in the internal portion and the housing to provide heating of the fluid in the internal portion.

TECHNICAL FIELD

The present disclosure relates to the field of systems and methods forgenerating heat. In particular, the present disclosure relates tosystems and methods which use a cell to provide a heated fluid.

BACKGROUND

Typically, the generation of power and/or heating may involve combustionof some sort of fuel. For instance, fossil fuels may be used in acombustion process which heats water to generate steam and/or hot water.Steam may be generated to be used for driving a turbine, and this inturn may be used to generate electricity. Hot water may be generated tobe used in heating systems, where that hot water is circulatedthroughout a building to provide heating to that building. Electricitycould also be used to generate warm water, such as in an electricboiler. It may be desirable to provide increased efficiency for suchgeneration of power and/or heating.

SUMMARY

Aspects of the disclosure are set out in the independent claims andoptional features are set out in the dependent claims. Aspects of thedisclosure may be provided in conjunction with each other, and featuresof one aspect may be applied to other aspects.

In an aspect, there is provided a heating system comprising: a liquidsupply system; a cell configured to: receive liquid from the liquidsupply system, provide heating thereof, and output heated fluid; a workextraction system configured to extract useable work from heated fluidoutput from the cell. The cell comprises: (i) a housing arranged todefine an internal portion for receiving liquid to be heated, and (ii) aplurality of electrodes configured to apply electrical energy to fluidin the internal portion. The electrodes are configured to applyelectrical energy to said fluid in the internal portion to generate oneor more bubbles of plasma for releasing energy into said fluid in theinternal portion and the housing to provide heating of the fluid in theinternal portion.

Embodiments may enable the provision of a high exergy heated fluid fromwhich work is extracted. Work may be extracted from this high exergyheated fluid to provide heating and/or power generation. Embodiments mayprovide an efficient system for generating heat and/or power. The cellmay comprise a plasma cell (e.g. a plasma-generating fuel cell).

The system may further comprise a controller configured to: (i) receivea signal indicative of at least one operational parameter of the cell,and (ii) control operation of the heating system based on saidoperational parameter. The controller may be configured to controloperation of the heating system so that heat and/or plasma generation inthe cell is above a threshold level. Controlling operation of theheating system may comprise controlling at least one of: (i) the supplyof liquid to the cell by the liquid supply system, and (ii) theelectrical energy applied by the electrodes. The controller may beconfigured to control operation to keep at least one operationalparameter for the cell within a selected range (e.g. to provide aselected level of performance for the cell).

The controller may be configured to control the supply of liquid to thecell and/or the electrical energy applied by the electrodes based on anobtained indication of demand for heating to be provided by the cell. Inthe event that the obtained indication of demand indicates increaseddemand for heating to be provided by the cell, the controller may beconfigured to increase at least one of: (i) the temperature of liquidsupplied to cell, (ii) the pressure of liquid supplied to the cell,(iii) the amount of liquid supplied to the cell, and (iv) the amount ofelectrical energy applied by the electrodes. For example, controllingsuch operation may facilitate an increase in the output of the cell(e.g. to provide more heated fluid and/or plasma generation within thecell).

The signal indicative of at least one operational parameter may comprisean indication of a quality and/or quantity of plasma generation withinthe cell. The controller may be configured to control operation of theheating system so that the quality and/or quantity of plasma generationremains within a selected range. For example, the controller may beconfigured to provide at least a threshold amount of plasma generation.This threshold amount/selected range for plasma generation may beselected so that sufficient plasma generation is occurring to provideselected heating characteristics for the heating system (e.g. so thatthe amount of heated fluid generated is within a selected range).

The signal indicative of a quality and/or quantity of plasma generationmay comprise an indication of at least one of: (i) a pressure and/ortemperature of fluid output from the cell, (ii) an amount and/or type ofelectromagnetic energy present within the cell, (iii) chatter associatedwith supply of power to one or more of the electrodes, (iv) a currentflow and/or voltage associated with one or more of the electrodes, and(v) fluid flow dynamics within the cell. For example, higher pressuresand/or temperatures (e.g. for fluid output from the cell) may indicateincreased plasma generation. Likewise, a higher rate of increase forpressure/temperature may indicate greater plasma generation. Forexample, an increase in any of: electromagnetic activity within thecell, and/or chatter associated with the supply of power may provide anindication of increased plasma generation. For example, sudden changesin current or voltage may provide an indication of any change in plasmageneration.

Where current begins to increase, this may provide an indication ofarcing being about to occur. For example, the controller may beconfigured to reduce, or stop, the application of voltage to the firstelectrode in the event that a change in current exceeds a thresholdvalue (or a rate of change of current exceeds a threshold), e.g. if thecurrent is increasing too much. For example, voltage may be monitored toidentify any drops in voltage, e.g. in response to arcing providingdecreased resistance to current flow. For example, an indication ofincreased turbulence for fluid flow within the cell may provide anindication of increased plasma generation.

The controller may be configured to control at least one of: (i) thesupply of liquid to the cell based on the electrical energy to beapplied by the plurality of electrodes, and (ii) the electrical energyto be applied by the plurality of electrodes based on the supply ofliquid to the cell. For example, when increasing the supply of liquidand/or electrical energy, the controller may control the supply ofelectrical energy/liquid (respectively) in accordance with the change tosupply of the other. The change in supply of one may be selected basedon the change of supply to the other (e.g. the increase/decrease in onemay be selected in proportion to the increase/decrease in supply of theother). The signal indicative of at least one operational parameter maycomprise an indication of a temperature associated with at least one of:the cell, the fluid in the cell, and the fluid output from the cell. Thecontroller may be configured to control at least one of: (i) theelectrical energy applied by the electrodes, (ii) the supply of liquidto the cell, and (iii) an external heater, to increase the temperatureof the cell, the fluid in the cell, and/or the fluid output from thecell in the event that the indication of temperature is below athreshold level. The controller may be configured to increase theelectrical energy applied by the electrodes to provide increased heatingand/or decrease the flow rate of liquid through the cell in the eventthat the indication of temperature is below the threshold level.

An internal surface of the housing of the cell may comprise anelectromagnetic energy-absorbing material arranged to convert incidentphotons into heat. At least a portion of the housing may be conductive.For example, the internal surface of the housing may be configured togenerate heat in response to photons being incident on said surface. Thehousing (e.g. its internal surface) may be configured to heat the fluidwithin the internal portion in response to generating heat from incidentphotons (e.g. and/or other particles such as electrons). The housing maybe configured to provide conductive heating of the fluid within theinternal portion. The housing may be made of metal, e.g. the housing maybe made of steel. The housing may be formed of a plurality of differentmaterials. One or more layers or sleeves may be provided to the housing.For example, the cell may include a sleeve located in the internalportion within the housing. The sleeve may be arranged to fit within theinternal portion (e.g. it may sit adjacent to the internal portion ofthe housing). A plurality of such sleeves may be provided. Each sleevemay be arranged to provide different absorption/conduction properties toother regions of the housing/cell. For example, the housing may be madeof a first material (e.g. steel), and a sleeve made of a second material(e.g. aluminium) may be inserted within the housing. The housing and/orsleeve may include a coating to further facilitate absorption and/orconduction. For example, a gold coating may be applied.

The liquid supply system may be configured to supply liquid to the cellunder pressure. The cell may be arranged to retain fluid in the housingunder pressure. For example, the housing may comprise one or morecompression devices configured to retain the internal portion of thehousing under pressure, and/or the housing may be sufficiently rigid toresist expansion under the pressure applied from inside the internalportion. The liquid supply system may be configured to heat liquid priorto supplying it to the cell. The liquid supply system may be configuredto increase heating of liquid prior to supplying it to the cell in theevent that heat and/or plasma generation of the cell is below athreshold level. The system may be arranged to provide a variablecontinuous supply of liquid to the cell.

The plurality of electrodes may comprise: (i) an anode arranged toprovide a conductive path for current to be applied to fluid in theinternal portion, and (ii) a cathode arranged to provide a conductivepath away from the internal portion for current received from the anodethrough the fluid in the internal portion. The plurality of electrodesmay further comprise a balancing electrode arranged to provide anadditional conductive path towards or away from fluid in the internalportion. The anode and cathode (and e.g. balancing electrode) may bearranged concentrically with each other. The anode, cathode andbalancing electrode may have the same coefficient of thermal expansion.The balancing electrode may be arranged away from the conductive pathbetween the anode and the cathode. For example, the conductive path fromthe anode to the cathode may be radially outward. The balancingelectrode may be offset from anode/cathode in a different direction(e.g. along a longitudinal axis). The balancing electrode may be closerto the anode than the cathode is. For example, the balancing electrodemay run substantially perpendicular (e.g. perpendicular) to the currentpath from anode to cathode (e.g. it may be parallel to the anode).

The cell may comprise a resistive element arranged between the anode andcathode, for example the resistive element may comprise quartz or abora-silicate glass material (e.g. a high resistance material which canwithstand high temperatures and/or pressures). The resistive element maybe of sufficient electrical resistance so that it may act as anelectrical insulator. The resistive element may be arranged between onthe conductive path between anode and cathode, e.g. to provide increasedelectrical resistance between anode and cathode. For example, theresistive element may be located radially outward from the anode, andradially inward from the cathode (e.g. where the conductive path fromanode to cathode extends radially outward).

The system may be configured to provide additional heating to one ormore components of the cell (e.g. during a start-up mode). The cell maycomprise a heating element to provide such heating. For example, aheater may be located adjacent to the cell, and/or a heating element maybe integrated within a part of the cell. A heater may be included in anend cap of the cell (e.g. a cartridge heater may be provided within anend cap of the cell). In some examples, this heating may be provided bya resistive heating element. The resistive heating element may be a partof the cell (e.g. voltage may be applied to a component such as anode orresistive element to provide resistive heating, or to an additionalresistive heating element or region of the cell). Such heating may beprovided to increase the temperature associated with at least one of:the cell, fluid inside the cell, and fluid output from the cell to thepoint where the plasma is stimulated. For example, heating may beprovided until bubbles being to appear (e.g. gas bubbles).

The liquid supply system may be configured to supply a fluid to thecell, such as water, which at least partially exhibits non-Newtoniannature under circumstances to be expected within the cell. For example,wherein the liquid is configured to resist rapid expansion of plasmawithin the cell. The system may further comprise a filter apparatusconfigured to filter fluid output from the cell. The work extractionsystem may comprise at least one of: (i) a regulator for mass transferof hot and/or pressurised fluid, (ii) a heat exchanger for transfer ofheat to a working fluid, and (iii) a power generation system such as asteam-based power generation system. The heated fluid generated by thecell may itself be used for subsequent applications, or may instead beused for heating one or more other fluids for subsequent applications.For example, heated fluid generated by the cell may be used as a workingfluid or heated fluid generated by the cell may be used to heat aseparate fluid, which may then be used as a working fluid. The systemmay comprise a DC voltage source operable to apply a DC voltage to eachof the electrodes.

In an aspect, there is provided a system comprising: a cell configuredto heat liquid provided thereto, the cell comprising: an inlet forreceiving a liquid to be heated, and an outlet for outputting heatedfluid; a power management system configured to control application ofelectrical energy to the cell to control the heating of fluid in thecell; a work extraction system coupled to the outlet and configured toextract useable work from heated fluid output from the cell; and a fluidmanagement system coupled to the inlet of the cell, and configured to:(i) supply liquid to be heated to the cell, and (ii) process heatedfluid which has been output by the cell and used by the work extractionsystem.

The cell may comprise a cell as disclosed herein. The work extractionsystem may comprise a work extraction system as disclosed herein. Thefluid management system may comprise a liquid supply system as disclosedherein, e.g. for supplying liquid to be heated to the cell.

The fluid management system may comprise: (i) a liquid supply couplingfor coupling the system to a supply of liquid to be heated, and (ii) adrain coupling for discarding heated fluid which has been output by thecell and used by the work extraction system. The fluid management systemmay comprise a pump coupled to the liquid supply coupling and the inletof the cell, wherein the pump is operable to supply liquid to the cellunder pressure. The work extraction system may comprise a heat engine.The outlet of the cell may be coupled to a first engine inlet to enableheated fluid output from the cell to drive the engine. The heat enginemay be coupled to a generator configured to generate power in responseto driving of the engine. The outlet of the cell may also be coupled toa first heat exchanger. A first engine outlet may be coupled to thefirst heat exchanger so that heated fluid from the cell which has passedthrough the engine is directed to the first heat exchanger for heating.The first heat exchanger may be coupled to a second engine inlet toenable reheated fluid from the heat exchanger to further drive theengine. The engine may be arranged to be driven at a different ratio forfluid entering through the first and second engine inlets. At least oneof the engine and the first heat exchanger may be coupled to a secondheat exchanger configured for further extracting heat from the heatedfluid output from the cell.

The fluid management system may comprise a filter for filtering heatedfluid which output from the cell. The work extraction system maycomprise at least one of: a heat management system configured to receiveheated fluid which has been output from the cell, and to use said heatedfluid as a heat source or in a heat exchanger; and a power generationsystem configured to receive heated fluid which has been output from thecell, and to use said heated fluid to generate power. The powergeneration system may be coupled to the power management system toprovide generated power thereto. The power management system maycomprise an external coupling for coupling to an external source ofpower. The power management system may be configured to receive powerfrom the external source and/or provide power generated by the powergeneration system to the external source.

In an aspect, there is provided a method of providing a heated fluid forextracting useable work therefrom, the method comprising: supplying aliquid to be heated to a cell, wherein the cell comprises: (i) a housingarranged to define an internal portion for receiving the liquid to beheated, and (ii) a plurality of electrodes configured to applyelectrical energy to fluid in the internal portion; controllingoperation of the plurality of electrodes to apply electrical energy tofluid in the internal portion to generate one or more bubbles of plasma;generating heat in the housing proximal to the internal portion inresponse to the housing receiving incident photons (e.g. and alsoelectrons) associated with plasma bubbles in the internal portion; usingthe housing to conductively heat fluid in the internal portion.

In an aspect, there is provided a method of controlling operation of aheating system, the heating system comprising a cell comprising: (i) ahousing arranged to define an internal portion for receiving liquid tobe heated, and (ii) a plurality of electrodes configured to applyelectrical energy to fluid in the internal portion, the methodcomprising: controlling operation of the electrodes to apply electricalenergy to fluid in the internal portion to generate one or more bubblesof plasma for releasing energy from the plasma into the fluid in theinternal portion and the housing to provide heating of the fluid in theinternal portion, wherein controlling operation of the electrodescomprises: receiving a signal indicative of at least one operationalparameter associated with the cell and/or a fluid associated therewith;operating in a ‘cold-start’ mode when the operational parameterindicates heating and/or plasma generation is below a threshold level;and operating in a ‘normal’ mode when the operational parameterindicates heating and/or plasma generation is above the threshold level;wherein operating in the cold-start mode comprises controlling at leastone of: (i) the electrical energy applied by the electrodes, (ii) supplyof liquid to the cell, and (iii) operation of an external heater, toincrease the temperature of the cell and/or the fluid associatedtherewith in the event that the operational parameter indicates heatingand/or plasma generation is below a threshold level.

Aspects of the present disclosure may also provide one or more computerprogram products comprising computer program instructions configured tocontrol a processor to perform any of the methods disclosed herein.

FIGURES

Some examples of the present disclosure will now be described, by way ofexample only, with reference to the figures, in which:

FIG. 1 shows a schematic diagram of an exemplary heating system.

FIG. 2 shows a schematic diagram of an exemplary heating system.

FIG. 3 shows a schematic diagram of an exemplary cell.

FIG. 4 shows a block diagram of an exemplary heat and power generatingsystem.

FIG. 5 shows a schematic diagram of an exemplary heat and powergenerating system.

In the drawings like reference numerals are used to indicate likeelements.

SPECIFIC DESCRIPTION

Embodiments of the present disclosure are directed to systems forgenerating heat and/or power. Such systems may provide heating of aliquid to produce a heated fluid. The heated fluid may then be used forheating purposes and/or for power generation purposes. To generate theheated fluid, liquid may be supplied to a cell. Electrical energy may beapplied to liquid held in the cell via one or more electrodes of thecell. The application of this electrical energy to the fluid within thecell causes gas bubbles within the cell to form plasma bubbles. Eachbubble of plasma will be a localised region having a higherpressure/temperature than its surrounding fluid. The surrounding fluidmay limit expansion of the plasma bubbles so that, as electrical energyis still applied, these bubbles will emit electromagnetic energy. Forexample, photons may be emitted from atoms (or molecules) within theplasma bubbles. In turn, these emitted photons may heat up the substanceon which they are incident. For instance, this may provide heating ofthe housing of the cell and/or fluid within the cell. In turn, thisenables the cell to output a heated fluid for using in a heating and/orpower generation system 500. The heated fluid may contain liquid and/orgas, and in some cases, the heated fluid may also contain some plasmaticmaterials.

An exemplary heating system will now be described with reference to FIG.1 .

FIG. 1 shows a schematic diagram of a heating system 50. The heatingsystem 50 includes a liquid supply system 10, a cell 100 and a workextraction system 20. The cell 100 includes a fluid inlet 12 and a fluidoutlet 22. The cell 100 has a housing 120 which defines an internalportion 125 of the cell 100. The cell 100 also includes a plurality ofelectrodes, which, as shown, includes a first electrode 111 and a secondelectrode 112. The cell 100 may comprise a plasma cell (e.g. aplasma-generating fuel cell).

The housing 120 of the cell 100 encapsulates the internal portion 125.The fluid inlet 12 provides a flow path for fluid into the internalportion 125 of the cell 100. The fluid outlet 22 provides a flow pathfor fluid out from the internal portion 125 of the cell 100. Theinternal portion 125 of the cell 100 may otherwise be sealed by thehousing 120. The liquid supply system 10 is coupled to the fluid inlet12 of the cell 100. The work extraction system 20 is coupled to thefluid outlet 22 of the cell 100. The couplings between the liquid supplysystem 10 and the fluid inlet 12, and the work extraction system 20 andthe fluid outlet 22 are shown as an annular flow path. However, it willbe appreciated that this is purely for illustrative purposes, and anysuitable flow path may be provided). Also, although not shown in theFigs., the work extraction system 20 may also be coupled to the liquidsupply system 10 (e.g. to facilitate heating and/or pressurising ofliquid to be supplied to the internal portion 125).

The first electrode 111 is at least partially disposed within theinternal portion 125 of the cell 100. The second electrode 112 may alsobe disposed at least partially within the internal portion 125 of thecell 100. The first and second electrode 112 are arrangedconcentrically. The first electrode 111 extends within a central regionof the internal portion 125 of the cell 100. The second electrode 112 isarranged radially outward from the first electrode 111. The secondelectrode 112 may be cylindrical, as may the first electrode 111. Thefirst and second electrode 112 are arranged co-axially in the exampleshown in FIG. 1 . The second electrode 112 is located adjacent to aninternal surface of the housing 120 (however in some examples, thesecond electrode 112 may be integrated with the housing 120, e.g. toform a part thereof, and/or a portion of the housing 120 may provide thesecond electrode 112, e.g. if said portion of the housing iselectrically conductive).

A first end of the first electrode 111 is located outside the internalportion 125 of the housing 120. A second end of the first electrode 111,distal to the first end, is located within the internal portion 125 ofthe housing 120. The second electrode 112 may extend along some, or all,of the length of the internal portion 125 of the housing 120. At leastone end of the second electrode 112 may extend out of the internalportion 125 of the cell 100. Although not shown in FIG. 1 the firstand/or second electrode 112 may each be coupled to a power supply. Forexample, each electrode may have one end which extends outside theinternal portion 125 (e.g. into the housing 120), and this end may becoupled to the power supply. In some examples, the housing 120 mayprovide a ground, and the first electrode 111 may be connected to apositive terminal of the power supply.

The housing 120 may be cylindrical. The fluid inlet 12 is arranged at anopposite end of the housing 120 to the fluid outlet 22. The first andsecond electrode 112 extend along an axis extending from the fluid inlet12 to the fluid outlet 22 (e.g. a longitudinal axis of the cell 100).The fluid outlet 22 may be arranged vertically higher (e.g. above, suchas directly above) the fluid inlet 12.

The liquid supply system 10 is arranged to supply liquid to the cell100. Liquid may be provided into the cell 100 through the fluid inlet12. The liquid supply system 10 may comprise a coupling to a liquidsupply, such as a reservoir of liquid. The liquid supply system 10 isconfigured to control delivery of this liquid to the cell 100. Forexample, the liquid to be supplied may comprise partly or wholly a fluidwhich exhibits non-Newtonian behaviour in the environment of the cell100. The liquid may be water or an aqueous solution.

The work extraction system 20 is arranged to receive heated fluid fromthe cell 100. Heated fluid may be output from the cell 100 through thefluid outlet 22. The heated fluid may comprise liquid and/or gas. Forexample, this may be a combination of gas and liquid—e.g. steam withsome water droplets. The fluid outlet 22 is arranged to enable flow ofthis heated fluid out from the cell 100 to be used by the workextraction system 20. For example, steam created within the cell 100 mayrise up and out through the fluid outlet 22. The work extraction system20 is configured to utilise the heated fluid output from the cell 100.The work extraction system 20 may be configured to receive this heatedfluid, and to use this as part of a supply of heated fluid (e.g. forheating purposes). The work extraction system 20 may be configured toreceive this heated fluid, and to use this heated fluid for generationof power. For example, this heated fluid may be used to drive agenerator, e.g. through use of a steam engine.

The housing 120 is configured to encapsulate the internal portion 125.The housing 120 is arranged to define the internal portion 125 toprovide a region in which liquid may be heated. An internal surface ofthe housing 120 (e.g. which faces/defines the internal portion 125) maybe configured to generate heat in response to incident photons (forexample, the housing 120 may be conductive). The internal surface maycomprise the region of the housing 120 which lies adjacent to theinternal portion 125. This may comprise part of the housing 120 and/orit may comprise an additional component, such as a layer/film providedthere to generate heat in response to incident photons. For example, theinternal surface may be configured to absorb electromagnetic energy,such as in the form of visible light. The internal surface is configuredto heat up as it receives incident photons. The internal surface isconfigured to provide heating of fluid within the internal portion 125,e.g. as it heats up from incident photons. The housing 120 may be madeof a metal, such as steel. The housing 120 is configured to retain fluidin the internal portion 125 under pressure.

The fluid inlet 12, the internal portion 125, and the fluid outlet 22are arranged to define a flow path for fluid to flow through theinternal portion 125 of the housing 120. The internal portion 125 isarranged to receive liquid to be heated through the fluid inlet 12. Thecell 100 is arranged to heat this liquid in the internal portion 125 toprovide a heated fluid. The fluid outlet 22 is arranged to provide aflow path for this heated fluid away from the internal portion 125.

The first and second electrodes 111, 112 are configured to provide acurrent flow path through the internal portion 125 of the cell 100. Oneof the electrodes 111, 112 may provide an anode, and the other mayprovide a cathode. For instance, the first electrode 111 may provide theanode for bringing current into the internal portion 125 of the cell100. The second electrode 112 may then provide the cathode for carryingcurrent away from the internal portion 125 of the cell 100. The firstand second electrode 112 are spaced apart from each other. The firstelectrode 111 is arranged to receive a voltage so that a potentialdifference exists between the first and second electrodes 111, 112. Thefirst and second electrodes 111, 112 are arranged capacitively. Thepresence of fluid in the internal portion 125 may provide a conductivepath between the first and second electrode 112. The fluid will provideelectrical resistance between the two electrodes 111, 112. The first andsecond electrode 112 with fluid in the cell 100 may effectively providea circuit having a capacitance and a resistance. The first and secondelectrodes 111, 112 are configured to provide a voltage stress to fluidand/or plasma within the internal portion 125.

In operation, the liquid supply system 10 supplies a liquid through thefluid inlet 12 and into the internal portion 125 of the cell 100. Inthis example, the liquid will be water, but other liquids may be used.The liquid supply system 10 operates to supply water to the cell 100 sothat the cell 100 fills up with water. Any gas previously in the cell100 may be forced out through the fluid outlet 22 of the cell 100. Thecell 100 may then be substantially filled with water.

A voltage is applied to the first electrode 111 (anode). This will causesome current flow into the water. Due to the electrical resistance ofwater, this current flow and resistance will cause some heating of thewater (e.g. 12R heating). This process of resistive heating continues asa voltage is applied to the first electrode 111. As the temperature ofthe water within the internal portion 125 rises, microbubbles of gaswill start to form within the water in the internal portion 125. Thesemay be steam bubbles forming or bubbles of air being released which weretrapped in the water supplied to the internal portion 125 of the cell100. As a result, some pockets of gas will develop within the liquid inthe internal portion 125 of the cell 100. With continued application ofthe voltage to the first electrode 111, bubbles of plasma will begenerated within the internal portion 125 of the housing 120. Thesebubbles will release energy into the surrounding fluid and the internalsurface of the housing 120. In turn this provides heating of the fluidwithin the internal portion 125.

Without wishing to be bound by theory, by applying the voltage to thefirst electrode 111, this will charge up the capacitor provided by thefirst and second electrode 112. As the fluid within the internal portion125 heats up, its permittivity may change, and this may change acapacitance of the cell 100 (e.g. between the first and secondelectrodes 111, 112). For example, when water is used, its permittivitywill decrease as it heats up (and then also when it becomes steam). Inparticular, where microbubbles of gas (e.g. steam) begin to form withinthe liquid in the internal portion 125, these will provide localisedregions of lower permittivity. This process may effectively provide apermittivity collapse in localised regions.

For example, where water is used, this difference in permittivitybetween bubbles forming in the water and the surrounding water may be afactor of approximately 40 (e.g. the capacitance per unit volume inthose bubbles may be 1/40^(th) of that of the surrounding water). Duringthis process, the volumetric energy density for fluid and/or plasmawithin the internal portion 125 will remain constant. Due to thepermittivity collapse within the bubbles of gas, capacitance willdecrease in this region. As the volumetric energy density remainsconstant and the capacitance decreases, the voltage per meter will riseaccordingly (e.g. to conserve energy as per E=½ CV²). For examples wherewater is used, the voltage per meter will rise by a factor ofapproximately √40.

Without wishing to be bound by theory, with electrical energy stillbeing applied to the first electrode 111, these microbubbles of gas (atlower density than surrounding liquid) will try to rapidly expand intotheir surroundings. However, the surrounding liquid will resist thisexpansion, e.g. due to the non-Newtonian nature of the liquid in theseconditions. This will cause the microbubbles to rapidly increase intemperature and pressure. In turn, their capacitance will furtherdecrease (e.g. causing an increased dV/dr), thereby giving rise tofurther increased voltage stress across the bubble. With sufficientvoltage stress across the bubble, ionization may occur leading to theformation of plasma within the bubble. Thus, one or more plasma bubblesmay form in the liquid in the internal portion 125. The plasma may be atan even lower density than the gas, and so with a voltage still appliedto the first electrode 111, the plasma bubble will further try torapidly expand. In particular, this process of plasma bubble generationwill occur rapidly, and so each bubble of plasma will drive for rapidexpansion. In turn, this will bring about non-Newtonian fluid responsesin the liquid in the internal portion 125 of the cell 100. For instance,where water is used, the water does not immediately yield before thepressure wave brought about by the bubble of plasma trying to expand.The bubble of plasma is therefore held in a relatively fixed volume(e.g. it may only expand relatively slowly). While the volume of theplasma remains relatively constant, the temperature and pressure withinthis bubble rise rapidly in response to the voltage stress brought aboutby the voltage applied to the first electrode 111.

Without wishing to be bound by theory, to accommodate this high level ofenergy within the plasma bubble, energy may be absorbed by atoms (andmolecules) within the bubble. The energy levels (e.g. states) of theseparticles may therefore rise. Within the plasma, atoms may have theirelectrons move to higher electron energy levels, and/or spin states forthese particles may change. For example, Hydrogen atom spin states maychange from their lower energy para-state to their higher energyortho-state. Molecules may also move to higher rotational and/orvibrational energy levels, and/or further splitting up of thesemolecules may occur. As a result, the atoms within each bubble will beat disproportionately high energy levels (e.g. as compared toconventional fluids/the fluid within the internal portion 125).

Without wishing to be bound by theory, photon emission from the plasmamay occur to accommodate for the high energy within the plasma.Electrons may move to lower energy electron states, and/or changes tolower energy vibrational/rotational/spin states may occur foratoms/molecules. It is this returning to lower energy configurationswhich gives rise to the emission of photons (e.g. to accommodate for thedrop in energy levels as per the Bohr model). This emission of photonsmay occur on a relatively large scale. Where water is used, a largeproportion of this photon emission occurs in the visible light spectrum.

The photons emitted from each plasma bubble will then be absorbed byeither fluid in the internal portion 125 or the housing 120 of the cell100. In response to receiving such incident photons, the fluid and/orhousing 120 will heat up as it absorbs said photons. The inner surfaceof the housing 120 in particular may absorb a large number of thesephotons and thus increase in temperature. As the inner surface of thehousing 120 heats up, it will in turn provide conductive heating of thefluid within the internal portion 125. This may give rise to convectioncurrents occurring and thus increased turbulence for fluid within theinternal portion 125 of the cell 100. As a result of this process, thefluid within the internal portion 125 will heat up. The majority of theliquid provided to the internal portion 125 of the cell 100 may thenevaporate to provide a gas (e.g. steam). It is to be appreciated in thecontext of the present disclosure that some of the fluid which exits thecell 100 may have somewhat unconventional, or at least lower energyconfigurations, as compared to the liquid that was provided to the cell100. This is as a consequence of the plasma generation and subsequentenergy release which occurred within the cell 100.

This heated fluid then passes through the fluid outlet 22. Typically,the heated fluid is in the form of steam, which is generated within theinternal portion, and which rises up and out through the fluid outlet22. The heated fluid is then used in the work extraction system 20 toextract useable work from the heated fluid. For instance, this heatedfluid may be used for power generation and/or heat distribution.

Further examples of the present disclosure will now be described withreference to FIG. 2 .

FIG. 2 shows a schematic diagram of a heating system 50. As with FIG. 1, the heating system 50 of FIG. 2 includes a liquid supply system 10, acell 100 and a work extraction system 20. These components of theheating system 50 of FIG. 2 are similar to those of FIG. 1 , e.g.features of the heating system 50 of FIG. 1 could be used in combinationwith features of the heating system 50 of FIG. 2 .

The liquid supply system 10 may additionally include a liquid reservoir14, a heater 16 and a pump 18. The cell 100 includes fluid inlet 12,fluid outlet 14, and housing 120 which defines an internal portion 125.The cell 100 includes first electrode 111 and second electrode 112.Also, as shown in FIG. 2 , the cell 100 may include a third electrode113 and a resistive element 115. The cell 100 may comprise a plasma cell(e.g. a plasma-generating fuel cell).

The heating system 50 may also include a power supply 30 and acontroller 40. A plurality of sensors are shown by black circles toillustrate possible sensing capabilities of the system 50. The sensorsshown include a power supply sensor 41, a fluid inlet sensor 42, a firstelectrode sensor 43, a second electrode sensor 44, and third electrodesensor 45, a fluid outlet sensor 46, and an internal portion sensor 47.

The liquid supply system 10 may couple the liquid reservoir 14 to thefluid inlet 12 of the cell 100. The liquid reservoir 14 may be coupledto the fluid inlet 12 via the pump 18 and/or the heater 16 (both areshown in FIG. 2 ). The liquid supply system 10 is configured to provideliquid to the internal portion 125 of the cell 100. The liquid supplysystem may supply liquid from a source of liquid, such as the liquidreservoir 14 shown in FIG. 2 , or it may comprise a coupling to a liquidsupply, e.g. a mains water supply, for supplying liquid.

The first and second electrode 112 may be arranged within the cell 100as described above with reference to FIG. 1 . Additionally, the thirdelectrode 113 is also provided in the internal portion 125 of the cell100. The third electrode 113 is optional, and may or may not beincluded. When included, a first end of the third electrode 113 may belocated outside the internal portion 125, and the third electrode 113may extend form the first end to a second end located within theinternal portion 125. The second end of the third electrode 113 may belocated proximal to the second end of the first electrode 111 within theinternal portion 125. The first and third electrodes 111, 113 may beparallel (e.g. they may be co-axial). The second and third electrodes112, 113 may be parallel (e.g. coaxial). The first electrode 111 mayextend from outside a first end of the housing 120 into the internalportion 125 towards an opposite end of the housing 120. The thirdelectrode 113 may extend from outside the opposite end of the housing120 into the internal portion 125 towards the first end. The first andthird electrodes 111, 113 may extend into the internal portion 125 sothat there is no spatial overlap between these electrodes 111, 113 (e.g.their respective second ends do not touch/overlap). The second electrode112 may extend along the length of the internal portion 125 from at oroutside the first end to at or outside the opposite end. The distancebetween the second end of the first electrode 111 and the second end ofthe third electrode 113 may be less than the smallest distance betweenthe first electrode 111 and the second electrode 112. The thirdelectrode 113 may be located away from an expected current path betweenthe first and second electrode 112.

A resistive element 115 may also be included in the internal portion125. The resistive element 115 may also be cylindrical. The resistiveelement 115 may be arranged to increase the electrical resistance of theconductive path between the first electrode 111 (anode) and the secondelectrode 112 (cathode). The resistive element 115 may extend around amajority of the internal portion 125 (e.g. along a length and width ofthe internal portion to impede the majority of possible conductive pathsfrom anode to cathode). The resistive element 115 may be located betweenthe first/third and second electrodes 111, 112. For example, theresistive element 115 may be located radially outward from thefirst/third electrodes 111, 113, but not as far radially outward thanthe second electrode 112. The resistive element 115 may extend alongsome or all of the length of the internal portion 125.

The resistive element 115 may be arranged on a current flow path betweenthe first electrode 111 and the second electrode 112, e.g. so thatcurrent would need to flow through the resistive element 115 to get fromthe first electrode 111 to the second electrode 112. The resistiveelement 115 may extend along one or both of the ends of the internalportion 125 (e.g. to reduce the likelihood of a conductive path fromanode to cathode not via the resistive element 115 being possible).

The power supply 30 may comprise a DC supply (e.g. there may be an AC toDC converter for providing DC). The power supply 30 may be coupled toone or more components of the heating system 50. FIG. 2 illustrates anumber of these possible couplings with solid lines.

For example, these may comprise some form of conductor to provide aconductive coupling from the power supply 30 to said component. Thepower supply 30 may be coupled to the first electrode 111, and/or any ofthe second electrode 112, or third electrode 113. The cell 100 may alsoinclude a heater, such as a resistive heater (e.g. a cartridge heater).The power supply may also be coupled to the heater. The power supply 30could be coupled to the resistive element 115 (e.g. to provide resistiveheating), as shown in FIG. 2 . However, it is to be appreciated that theresistive element need not be coupled to the power supply.

Instead, it may be included only to increase resistance between firstand second electrodes 111, 112.

The controller 40 may be coupled to each of the sensors. The controller40 may also be coupled to one or more of the power supply 30, the heater16 and the pump 18. FIG. 2 illustrates these couplings with dashedlines. These couplings may be wired or wireless.

The liquid supply system 10 is configured to supply liquid to theinternal portion 125 of the cell 100. The controller 40 may beconfigured to control operation of the liquid supply system 10. Forexample, the liquid supply system 10 may selectively heat (using theheater 16) and/or pressurise (using the pump 18) liquid from the liquidreservoir 14 which is to be provided to the internal portion 125 of thecell 100. The controller 40 may be configured to control operation ofthe heater 16 and/or pump 18 to control the temperature and/or pressureof the liquid supplied to the cell 100.

The power supply 30 may be configured to apply a voltage to the firstelectrode 111 (e.g. to provide the operation described above withreference to FIG. 1 ). The power supply 30 may also be configured toapply a voltage to the third electrode 113 (and/or e.g. a heater of thecell 100). The power supply 30 may also be coupled to the secondelectrode 112 to receive a current carried away therefrom. The powersupply 30 may be configured to selectively apply a voltage, e.g. usinghigh voltage DC. The controller 40 may be configured to controloperation of the power supply 30. For example, the controller 40 may beconfigured to control at least one of: a magnitude of voltage applied bythe power supply 30, timing for the voltage supply, and/or thecomponents to which voltage is being applied.

The third electrode 113 may be active or passive. When active, a voltageis applied to the third electrode 113. When passive, the third electrode113 may be conductive for receiving current within the internal portion125, but without receiving power from the power supply 30.

The third electrode 113 may be configured to provide a balancingelectrode (e.g. it may be arranged to balance electric field/currentgenerated within the internal portion 125). The controller 40 may beconfigured to control operation of the power supply 30 to selectivelycontrol whether (and/or how much) voltage is applied to the thirdelectrode 113.

The resistive element 115 may be configured to be of relatively highresistance (e.g. as compared to the resistance of the electrodes and/orfluid within the internal portion 125). The resistive element 115 may beof sufficient resistance to effectively provide an electrical insulator(between the anode and cathode).

In examples, the cell includes a heater configured to provide heating inresponse to application of a voltage thereto, e.g. to provide resistive(I²R) heating. The heater could be a region of the housing, or aseparate component configured to provide resistive heating (e.g. whichmay be integrated into a part of the housing, such as an end cap). Theheater could be arranged to provide heating of the fluid in the internalportion 125 and/or the housing 120 in response to application of avoltage thereto. The controller 40 may be configured to controloperation of the power supply 30 to selectively control whether (and/orhow much) voltage is applied to the heater. In some examples, the heatercould be provided by the resistive element 115.

The controller 40 may be configured to receive a signal indicative of atleast one operational parameter of the operation of the cell 100. Thecontroller 40 may be configured to control operation of the heatingsystem 50 based on this received signal. For example, the controller 40may be configured to control operation of at least one of the heater 16,the pump 18, and/or the power supply 30 based on the received signal.The controller 40 may be configured to control the heat and/or pressureof liquid supplied to the internal portion 125. The controller 40 may beconfigured to control whether and/or how much voltage is applied to oneor more of the first electrode 111, the third electrode 113 and/or theheater. In other words, the controller 40 may be configured to controlthe supply of liquid to the internal portion 125 of the cell 100 and/orthe electrical energy to be applied by electrodes of the cell 100.

The controller 40 may be configured to control operation based on atleast one received signal indicative of one or more operationalparameters of the cell 100. The signal may be received from one or moreof the sensors. It is to be appreciated that the exact nature of thesignal received, and/or the sensor from which it is received is not tobe considered limiting.

Exemplary sensors are shown in FIG. 2 , which may provide informationindicative of one or more operational parameters of the system 50.

The power supply sensor 41 may be configured to provide an indication ofoperation of the power supply 30. The power supply sensor 41 may beconfigured to provide an indication of a magnitude of power (e.g.voltage) being applied, and/or it may provide any relevant feedback onthe signal being applied by the power supply 30. For example, the powersupply sensor 41 may be configured to provide an indication of anychatter associated with the voltage being applied by the power supply 30(e.g. to the first sensor). The fluid inlet sensor 42 may be configuredto provide an indication of at least one property of the liquid to besupplied to the internal portion 125. For example, this may comprise anindication of a pressure and/or a temperature of the liquid to besupplied. As another example, the fluid inlet sensor 42 may beconfigured to provide an indication of one or more chemical propertiesof the liquid to be supplied to the internal portion 125 (e.g.indicative of the chemical composition of said liquid, such aspercentage of impurities/additives etc.). The fluid outlet sensor 46 maybe similar to the fluid inlet sensor 42. For example, the fluid outletsensor 46 may be configured to provide an indication of a temperature,pressure and/or chemical composition of fluid being output from the cell100. The fluid outlet sensor 46 may be configured to provide anindication of any relevant energy configuration changes to the fluidexiting the cell 100 (e.g. whether any additional compositions arepresent).

The first electrode sensor 43, the first electrode sensor 44 and thethird electrode sensor 45 may be configured to provide an indication ofone or more properties of the relevant electrical energy presentthereat. The sensors may provide an indication of a voltage and/orcurrent present at the relevant electrode. For example, an electrodesensor may be configured to provide an indication of how current and/orvoltage at said electrode varies with time (e.g. to provide anindication of a time derivative for the current/voltage).

The internal portion sensor 47 is configured to provide an indication ofthe conditions within the internal portion 125 of the cell 100. Theinternal portion sensor 47 may be located within the internal portion125 of the housing 120, e.g. it may be attached to an internal wall ofthe housing 120 (as shown in FIG. 2 ). Alternatively, the internalportion sensor 47 may be located outside the external portion butconfigured to provide some indication as to the conditions within theinternal portion 125. The internal portion sensor 47 may be configuredto provide an indication of fluid flow dynamics within the internalportion 125—e.g. to provide an indication of whether there is anyturbulent flow, and/or how turbulent the flow is. This could include useof a flow meter, a microphone, or any other suitable sensor. Theinternal portion sensor 47 may be configured to provide an indication ofelectromagnetic energy present inside the internal portion 125 (e.g. anindication of the amount and/or type of electromagnetic emissionoccurring). For example, the internal portion sensor 47 may comprise asuitable antenna to detect the presence of such electromagneticenergy/emissions, and/or it may comprise some form of camera (e.g. aspart of a fibre optic) configured to obtain an indication of lightpresent in the cell 100. The internal portion sensor 47 may beconfigured to provide an indication of the state of activity occurringinside the cell 100.

In operation, the heating system 50 of FIG. 2 functions in much the samemanner as the heating system 50 described above with reference to FIG. 1. That is, the power supply 30 applies electrical energy (e.g. avoltage) to the first electrode 111 to heat the fluid in the internalportion 125. This heating is brought about by resistive heating and alsoheating from incident light emitted from bubbles of plasma within theinternal portion 125. Additionally, a capacitance may be providedbetween the first and third electrode 113, and/or between the second andthird electrode 113. This may provide a balancing effect to the electricfield within the internal portion 125 of the cell 100. The thirdelectrode 113 may provide a balancing effect if provided as a floatingelectrode (e.g. in a passive state) and if a voltage is applied to thethird electrode 113 (e.g. in an active state).

Additionally, the controller 40 may be configured to control operationof the heating system 50 according to any of a number of differentcontrol loops. Each control loop may provide a feedback loop in whichdata indicative of an operational parameter of the cell 100 is obtained(e.g. from a sensor), and the controller 40 controls operation of acomponent of the heating system 50 based on this obtained data. The datamay be obtained from any suitable sensor (e.g. any of the sensors shownin FIG. 2 and described above). The controller 40 may control operationof any suitable component of the heating system 50, such as controllingthe supply of liquid to the internal portion 125 of the cell 100 (e.g.controlling the heater 16 or the pump 18), and/or controlling theelectrical energy to be applied by one or more of the electrodes (e.g.controlling the power supplied by the power supply 30).

Four exemplary control loops will now be discussed. In a first example,operation of the cell 100 will be described in a ‘normal’ mode, where atleast one property is monitored and/or regulated to provide increasedefficiency for operation of the cell 100. In second and third example,operation of the cell 100 will be described for increasing anddecreasing cell 100 output respectively. In a fourth example, operationof the cell 100 will be described when in a ‘start-up’ mode.

In the first example, operation of the heating system 50 is controlledin a normal mode of continued operation. Here, the controller 40 isconfigured to receive a signal indicative of an operational parameter ofthe cell 100, and the controller 40 is configured to control operationof the system 50 so that the operational parameter remains within adesired range for performance of the cell 100. The cell 100 is designedto provide heated fluid as its output. The operational parameter maytherefore provide an indication of the output for the cell 100. Forexample, the operational parameter may provide an indication of howefficiently the cell 100 is performing and/or an indication of themagnitude of heat generation being provided by the cell 100 (e.g. it mayprovide an indication of the amount/temperature of heated fluid beinggenerated by the cell 100 per unit time). It will be appreciated in thecontext of the present disclosure that the cell performance need not bedetermined per se., but instead, the controller 40 may control operationof the cell 100 based on an indicator of cell performance.

The controller 40 may be configured to receive an indication of cellperformance. The indication of cell performance may provide anindication of the operating state of the cell 100. This may comprise anindication of the amount/temperature of heated fluid being generated bythe cell 100 and/or an indication of the quality of plasma generationoccurring within the cell 100. The indicator may be based on atemperature and/or pressure of heated fluid being generated by the cell100 (e.g. it may be an indication of said temperature and/or pressure).For example, such an indication may be obtained using the fluid outletsensor 46. The indication may be based on both the temperature/pressureof liquid being provided to the cell 100 (e.g. as sensed by the fluidinlet sensor 42) and the temperature/pressure of heated fluid exitingthe cell 100 (e.g. as sensed by the fluid outlet sensor 46). Theindication may be based on an amount of heating being provided by thecell 100 (e.g. a difference between inlet and outlet temperatures),and/or a rate of heating being provided by the cell 100.

As an example, the controller 40 may be configured to receive a signalindicative of a temperature of the heated fluid leaving the cell 100. Inthe event that the heated fluid is outside a selected range (e.g. abovean upper threshold temperature and/or below a lower thresholdtemperature), the controller 40 may control operation of the heatingsystem 50 to increase/decrease the temperature, as appropriate, for theoutlet temperature to return to within the selected range. This mayfurther comprise the controller 40 determining if the liquid provided tothe cell 100 is heated by above a threshold amount and/or within athreshold time period. The controller 40 may control operation of theheating system 50 so that a sufficient amount of heating and/orsufficiently quick heating occurs.

In addition, or as an alternative, to receiving a direct indication of atemperature/pressure of heated fluid leaving the cell 100, thecontroller 40 may receive a signal which is indicative of cellperformance. For example, the controller 40 may receive a signalindicative of an amount and/or quality of plasma generation occurringwithin the cell 100. The controller 40 may control operation of theheating system 50 to so that the quantity and/or quality of plasmageneration occurring is within a selected range. In turn, this may actto control the generation of heated fluid by the cell 100, as thegeneration of plasma within the cell 100 ultimately gives rise toheating of the fluid within the cell 100.

The controller 40 may be configured to obtain an indication of aproperty of plasma generation within the cell 100 based on a receivedsignal from a sensor. The indication of the property of plasmageneration may be determined based on temperature and/or pressure datafor fluid entering and/or leaving the cell 100. The amount of plasmageneration may be determined based on the amount of heat generation,and/or the speed with which fluid is being heated. For example,quicker/more heating may indicate more plasma generation. The controller40 may be configured to determine that plasma generation is within aselected range in the event that the amount and/or rate of heating bythe cell 100 is within a selected range.

The amount of plasma generation may be determined based on an obtainedindication of the conditions inside the internal portion 125 of thehousing 120 (e.g. using the internal portion sensor 47). An indicationthat fluid within the internal portion 125 is moving turbulently mayindicate more plasma generation (e.g. due to more conduction heatingbeing provided by the inner portion of the housing 120, and this givingrise to convection currents). Alternatively, or additionally, anindication that more electromagnetic energy is present (e.g. more lightis visible/more electromagnetic waves are being detected) may indicatemore plasma generation. The controller 40 may be configured to determinethat plasma generation is within a selected range in the event that theamount of turbulence and/or electromagnetic energy/emissions is within aselected range.

The amount of plasma generation may be determined based on an obtainedindication of current and/or voltage at one of the electrodes. Forexample, the controller 40 may obtain an indication of a voltage beingapplied to the first electrode 111, and an indication of a resultingcurrent passing through the first electrode 111 (e.g. using the firstelectrode sensor 43). The controller 40 may be configured to monitorvoltage and current data over time and to determine based on thisvoltage and current data when a satisfactory plasma is generated. Forexample, the controller 40 may control the power supply 30 to increasethe voltage applied to first electrode 111 over time, and the controlmay monitor the resulting current. As the voltage increases, the currentwill also increase initially before holding relatively stable as thevoltage continues to increase. Once a threshold voltage is reached, thecurrent will begin to increase, and the rate of increase in current willincrease with increased voltage. The controller 40 may be configured todetect that satisfactory plasma generation has occurred in the regionwhere the current starts increasing again. For example, the controller40 may be configured to determine satisfactory plasma generation hasoccurred once the current begins to rise again. The controller 40 maythen control the power supply 30 to no longer raise the voltage appliedto the first electrode 111.

The amount of plasma generation may be determined based on an indicationof chatter being provided to the power supply 30 in response to applyinga voltage to the first electrode 111. For example, this may provide anindication of plasma generation occurring in the fuel, e.g. asvibrations occur due to plasma generation. The controller 40 may beconfigured to determine that plasma generation is within a selectedrange in the event that detected chatter is within a selected range.

The above examples describe operational parameters of the cell 100 whichthe controller 40 may be configured to determine and/or receive signalsindicative thereof. Based on obtaining an indication of any of theseoperational parameters, the controller 40 may be configured to controloperation of the heating system 50. In the event that the obtainedindication is outside a selected range (e.g. above an upper thresholdvalue and/or below a lower threshold value), the controller 40 maycontrol operation of the system 50 so that a value for that parameter iswithin the selected range. For this, the controller 40 may control theliquid supplied to the cell 100 and/or the electrical energy applied tothe fluid within the cell 100. The controller 40 may be configured tocontrol the liquid supplied to the cell 100 so that the at least oneoperational parameter is within a selected range. Controlling the liquidsupply may comprise at least one of: (i) controlling a temperature ofliquid supplied to the internal portion 125 of the cell 100, (ii)controlling a pressure of liquid supplied to the internal portion 125 ofthe cell 100, and/or (iii) controlling an amount of liquid supplied tothe internal portion 125 of the cell 100 within a selected time window.The controller 40 may be configured to control operation of the heater16 and/or the pump 18 to control the temperature and/or pressure of theliquid supplied to the cell 100. The fluid inlet 12 may comprise oneaperture for receiving liquid, or it may comprise a plurality, e.g. toprovide a plurality of entry points for liquid to flow into the cell.The controller 40 may be configured to control operation of the pump 18to control the flow rate of fluid through the cell 100, e.g. to controlhow much fluid is delivered to the cell 100 per unit time. The liquidsupply system 10 may be configured to provide a continuous flow ofliquid to the cell 100, and the controller 40 may control the rate atwhich liquid is supplied to the cell 100.

In the event that the operational parameter indicates that increasedoutput is needed from the cell (e.g. that the cell 100 needs to providemore heating of fluid), the controller 40 may control the liquid supplysystem 10 to provide at least one of: (i) liquid to the cell 100 at ahigher temperature, (ii) liquid to the cell 100 under higher pressure,and/or (iii) more liquid to the cell 100. For example, if theoperational parameter indicates that plasma generation is below athreshold, the control may increase the heat and/or pressure provided tothe cell 100.

The controller 40 may be configured to control the electrical energyapplied to electrodes of the cell 100 so that the at least oneoperational parameter is within the selected range. This may comprise atleast one of: (i) controlling the amount of time for which a voltage isapplied to the first electrode 111, (ii) controlling the voltage appliedto the first electrode 111, (iii) controlling the voltage applied to thesecond electrode 112, and/or (iv) controlling the voltage applied to theheater. Where the operational parameter indicates that temperaturegeneration needs to increase and/or plasma generation is below athreshold, the controller 40 may control the power supply 30 to increasethe energy applied. For example, if plasma and/or heat generation isbelow a threshold value, the controller 40 may apply a voltage (or applya larger voltage) to the heater and/or the first electrode 111.

The controller 40 may be configured to control both the electricalenergy to be applied by the electrodes of the cell 100 and the liquidsupply to the cell 100 (e.g. the two may be controlled simultaneously).The controller 40 may control one in dependence on how it is controllingthe other. For example, the controller 40 may select how to control theelectrical energy to be applied by the electrodes of the cell 100 basedon how it will control the liquid supply to the cell 100 (and/orvice-versa). In the event that the controller 40 determines thatincreased plasma generation is required, the controller 40 may increasethe voltage applied to the heater and/or first electrode 111, as well asincreasing the temperature and/or pressure of water to be provided tothe cell 100. In the event that the controller 40 determines thatincreased production of heated fluid is required, the controller 40 mayincrease the voltages applied to the electrodes and/or heater, as wellas to increase the amount of liquid supplied to the cell 100.

In the second and third examples, the controller 40 is configured toreceive a demand signal indicative of a demand on the output from thecell 100. The demand signal may indicate that more or less output isrequired from the cell 100. For example, this demand may be independentof the efficiency of cell 100—the cell 100 may be operating within athreshold range for a relevant operational parameter, but the demandsignal may indicate that the output needs to change (e.g. increase ordecrease).

In the event that the demand signal indicates less output is required,the controller 40 is configured to control the liquid supplied to thecell 100 and the electrical energy applied to the electrodes of the cell100. As the demand decreases, the controller 40 will decrease the supplyof liquid to the cell 100. For example, the controller 40 may decreasethe fluid flow rate through the cell 100. The liquid may still besupplied to the cell 100 at the same, or similar, temperature and/orpressure. The controller 40 may reduce the electrical energy to beapplied. For example, the controller 40 may decrease the voltage appliedto the first electrode 111. The controller 40 may still supply the same,or similar, voltage to the third electrode 113 and/or heater. Thecontroller 40 may still control operation, e.g. as described above, sothat plasma generation is within a selected range despite the totaloutput being decreased.

In the event that the demand signal indicates more output is required,the controller 40 may control operation in the opposite way. Thecontroller 40 may increase the rate that liquid is supplied to the cell100 and the amount of electrical energy applied to the electrodes of thecell 100. The controller 40 may be configured to control operation ofthe cell 100 to avoid a flow rate of liquid through the cell 100exceeding a plasma-generation threshold amount at which the flow rate istoo high for sufficient plasma generation to occur. The controller 40may still control operation, e.g. as described above, so that plasmageneration is within a selected range despite the total output beingincreased.

In the fourth example, the controller 40 is configured to controloperation of the system 50 in a start-up mode. For example, when thecell 100 is first turned on, it may take some time before it can beoperated at higher efficiencies. In particular, the housing 120 of thecell 100 may be colder than it would during use. The controller 40 maybe configured to determine that start-up operating conditions are to beused. For example, the controller 40 may obtain an indication oftemperature for relevant components of the system 50 (e.g. the housing120) to determine if the system 50 should operate in a start-up mode,and/or the controller 40 may determine based on an indication ofprevious use (e.g. that the system 50 has not been used recently) thatstart-up mode is to be used.

In start-up mode, the controller 40 is configured to control operationof the cell 100 to provide additional heating. The controller 40 mayincrease the voltage applied to the first electrode 111 to provideadditional resistive heating. Additionally, or alternatively, thecontroller 40 may apply a voltage to the heater e.g. to provideresistive heating. For example, the controller 40 may control operationso that a greater voltage is applied to the heater when in the start-upmode than during normal operation (e.g. no voltage may be applied to theheater during normal operation). For example, the controller 40 may beconfigured to control operation of the heater to provide more heatingduring start-up (e.g. more heating energy may be used).

The controller 40 may also control operation of an additional heater,such as a cartridge heater, to provide heating of the cell 100/internalportion 125. The controller 40 may control the supply of liquid to thecell 100 so that liquid supplied to the cell 100 is at a highertemperature and/or pressure and/or the flow rate of fluid through thecell 100 is lower when in start-up mode. The controller 40 may controlthe electrical energy applied to the electrodes and/or heater to behigher when in start-up mode.

The controller 40 may be configured to monitor at least one operationalparameter of the cell 100 to determine when to leave start-up mode. Forexample, while an obtained indication of a temperature associated withthe cell 100 remains below a threshold temperature value, the controller40 may control operation of the system 50 to be in start-up mode. Oncethis temperature exceeds the threshold temperature value, the controller40 may control operation of the system 50 to operate in normal-modeoperating conditions. For example, less pre-heating of liquid may occurwhen in the normal-mode. The controller 40 may be configured todetermine that sufficient plasma generation is occurring (e.g. in themanner described above), and in response to this, switch to thenormal-mode of operation.

Another exemplary cell 100 will now be described with reference to FIG.3 . The cell 100 of FIG. 3 corresponds closely to that previouslydescribed, and so description of relevant components will not berepeated.

FIG. 3 shows a cell 100. The cell 100 includes a first electrode 111, asecond electrode 112, a third electrode 113 and a resistive element 115.The cell 100 also includes a housing 120 which defines an internalportion 125, and which has a fluid inlet 12 and a fluid outlet 22. Thecell 100 also includes a first end cap 122, a second end cap 124 and acompression device 126. The cell 100 may comprise a plasma cell (e.g. aplasma-generating fuel cell).

The internal portion 125 extends from a first end of the housing 120,which includes the fluid inlet 12, to a second end of the housing 120,which includes the fluid outlet 22. The internal portion 125 may becylindrical. The housing 120 encapsulates the internal portion 125 apartfrom defining the fluid inlet 12 and the fluid outlet 22. In thisexample, the resistive element 115 lies adjacent to the internal wall ofthe housing 120 although in other examples, the resistive element 115may be integral with the internal wall or separate from the wall andinside the internal portion 125. The first end cap 122 and second endcap 124 may also form part of the resistive element 115—e.g. they alsoprovide increased resistance to a conductive path from anode to cathode.The second electrode 112 is arranged within (e.g. integral with) theinternal wall of the housing 120. The first and third electrode 113 sare disposed at least partially within the internal portion 125. Thefirst electrode 111 extends from outside the first end and into theinternal portion 125. The third electrode 113 extends from outside thesecond end and into the internal portion 125. There is a gap between thetwo in the internal portion 125. The three electrodes and the resistiveelement 115 may be coaxial (e.g. they may be concentric).

The first end cap 122 encloses the internal portion 125 at the firstend. The second end cap 124 encloses the internal portion 125 at thesecond end. The end caps 122, 124 form part of the housing 120 for theinternal portion 125. The first end cap 122 is non-conducting. Thesecond end cap 124 is non-conducting. Each end cap may effectively formpart of a resistive barrier for a conductive path from the anode to thecathode (e.g. the end caps may form part of, or work in combinationwith, the resistive element 115). Each end cap 122, 124 includes one ormore apertures to enable flow of fluid therethrough. One or both endcaps may have an aperture near to its centre. For example, theaperture(s) in the first end cap 122 may be located proximal to thefirst electrode 111. The aperture(s) may be arranged to facilitate flowof liquid into the internal portion 125 while inhibiting the likelihoodof a conductive path forming from the anode to the cathode through saidaperture(s). The first end cap 122 may have a plurality of apertures tofacilitate multiple different points through which liquid may flow intothe internal portion 125. The compression device 126 is located withinthe first end of the housing 120 adjacent to the first end cap 122. Thecompression device 126 may comprise any suitable biasing means, such asa spring. Each end of the housing 120 may have thicker material, asshown in FIG. 3 . At least one portion of the housing 120 may beconnected to electrical ground. As shown in FIG. 3 , the first end ofthe housing 120 is grounded. One or both of the end caps may include aheating element (e.g. a resistive heater), which may be used to provideheating to liquid within the internal portion 125 (e.g. duringstart-up). For example, the power supply 30 may couple to a heater inthe end cap (e.g. in the first end cap 122). The controller 40 may beconfigured to control application of power to the heater in the end capto provide heating.

The first electrode 111 may include a conductor extending along thelength of the electrode. The conductor may be provided within aninsulating body to provide the electrode. An insulating shroud may beprovided for at least some of the region of the electrode within theinternal portion 125 (e.g. the insulating shroud may be provided at theend of the first electrode 111 which is disposed in the internal portion125). For example, the electrode may have a conductor extending along acentral axis, where that conductor is radially surrounded by aninsulator along the length of the conductor being in the internalportion 125 (e.g. it may be along the entire length). The firstelectrode 111 may also include a carrier at its end away from theinternal portion 125. The carrier may comprise suitable fixing means,such as a ledge, for attachment to the first end cap 122. The carriermay comprise a sealing means and attachment means for attaching thefirst electrode 111 to the first end cap 122 and sealing the internalportion 125. For example, a radially extending flange may provide asealing face. For example, a screw thread may enable the end cap 122 tobe secured to the electrode to seal the internal portion 125. A similararrangement may be provided for the third electrode 113, and e.g. itsarrangement with the second end cap 124.

The compression device 126 is configured to apply pressure on the firstend cap 122 towards the internal portion 125 of the housing 120. Thecompression device 126 may facilitate retaining the internal portion 125of the housing 120 under pressure. The housing 120 is arranged to enablethe flow of liquid into the internal portion 125 through the fluid inlet12 and a flow of steam/liquid out through the fluid outlet 22. Thehousing 120 is arranged to provide structural support to enable theinternal portion 125 to be held under pressure with fluid therein. Forexample, the side wall(s) of the housing 120 is arranged to withstandradial expansion of the internal portion 125, and the end walls of thehousing 120 are arranged to withstand longitudinal expansion of theinternal portion 125. Operation of the cell 100 is similar to thatdescribed above with reference to FIGS. 1 and 2 , and so shall not bedescribed again here.

Heating systems described herein may find use in larger generationsystems. Examples of such larger generating systems will now bedescribed with reference to FIGS. 4 and 5 .

FIG. 4 shows a heat and power generating system 1000. The heat and powergenerating system 1000 comprises a power management system 200, a cell100, a heat management system 300, a fluid management system 400, and apower generation system 500. Also shown in FIG. 4 is a mains coupling220. The cell 100 may comprise a plasma cell (e.g. a plasma-generatingfuel cell).

FIG. 4 shows a block diagram to illustrate the functionalinterrelationship between the different component systems of the heatand power generating system 1000. However, it is to be appreciated thatthis is intended to demonstrate the functional connections, rather thanspecific structural connections. It will be appreciated that thestructural arrangement of the different component systems may beinterlinked (e.g. as will be described later with reference to FIG. 5 ).

As shown in FIG. 4 , the power management system 200 is coupled to thecell 100. The cell 100 is coupled to the heat management system 300. Theheat management system 300 is coupled to each of the power generationsystem 500 and the fluid management system 400. The fluid managementsystem 400 is coupled to the cell 100. The power generation system 500is coupled to the power management system 200. This coupling is intendedto demonstrate the functional interrelationships between the differentcomponent systems. The power management system 200 may also be coupledto the mains coupling 220 (e.g. as shown in FIG. 4 ).

The power management system 200 is configured to control the applicationof power to the cell 100. The power management system 200 may controlthe electrical energy (e.g. voltage) applied to the first electrode 111of the cell 100. The power management system 200 may also control theelectrical energy (e.g. voltage) applied to the remaining electrodesand/or the heater of the cell 100. The power management system 200 mayalso control operation of any pump 18 and/or heater 16 for providingliquid to the cell 100 under pressure and/or at a higher temperature.The power management system 200 may therefore control the operation ofthe cell 100 to generate heated fluid.

The cell 100 is configured to operate as described above (e.g. to applyelectrical energy inside its internal portion 125 to generate heatedfluid).

The heat management system 300 is configured to receive the heated fluidgenerated by the cell 100. The heat management system 300 is configuredto utilise this heated fluid to provide relevant thermal work. Forexample, the heat management system 300 may be configured to provideheating using this heated fluid, e.g. for heating buildings etc. Theheat management system 300 may comprise one or more components forproviding heat transfer from the heated fluid from the cell 100 toanother component and/or substance. For example, the heat managementsystem 300 may comprise one or more heat exchangers.

The power generation system 500 is configured to receive the heatedfluid generated by the cell 100. The power generation system 500 isconfigured to utilise this heated fluid to generate power (e.g.electrical energy). FIG. 4 shows the output of the cell 100 beingprovided to the heat management system 300, and from the heat managementsystem 300 to the power generation system 500. However, it will beappreciated in the context of the present disclosure that one of thesesystems may not be included, or the two systems may be provided by thesame components. The power generation system 500 may comprise one ormore generators to generate electricity based on movement of the heatedfluid (e.g. using pressurised gas to drive a turbine to generateelectricity). This arrangement may also include some heat management(e.g. to distribute heat to other parts of the power generation system500. In some examples, the heated fluid may be used for heating purposesand for power generation purposes. The heat management system 300 maythen control distribution of the heated fluid accordingly (e.g. tocontrol distribution of heated fluid to the power generation system500). For example, the work extraction system 20 described above maycomprise such a heat management system 300 and/or power generationsystem 500.

Power generated by the power generation system 500 may then be suppliedto the power management system 200. For example, this power generated bythe power generation system 500 may in turn be used by the powermanagement system 200 to power the cell 100 to provide further powergeneration. The power management system 200 may also be coupled to themains coupling 220 to receive and/or transmit power to the mains. Forexample, during start-up mode, the power management system 200 mayobtain all of its power from the mains, but after start-up, at leastsome of its power may be received from the power generation system 500.After start-up, some of the power generated by the power generationsystem 500 may be provided to the mains coupling 220 for distributionelsewhere.

The fluid management system 400 is configured to provide liquid to thecell 100 (e.g. as described above for the liquid supply system 10). Thefluid management system 400 is configured to receive fluid which hasbeen output from the cell 100. The fluid management system 400 may beconfigured to process fluid which was heated by the cell 100, and whichhas since been used by the heat management and/or power generationsystems. The heated fluid generated by the cell 100 may be at hightemperature and/or pressure. The heat management and/or power generationsystems are configured to extract useable work from this hightemperature/pressure fluid. Once the useable work has been extracted,the fluid may be at much lower temperatures and pressures. For example,it may leave the cell 100 as high temperature and pressure gas, and oncefully used for work extraction it may be liquid again (e.g. at a lowertemperature). The fluid management system 400 is configured to processthis used fluid. Processing the used fluid may comprise returning it tothe environment and/or processing (e.g. filtering) the fluid, e.g. sothat it could be used again as a liquid to be provided to the cell 100.

In operation, the power management system 200 receives power (e.g. fromthe mains coupling 220 and/or the power generation system 500). Thepower management system 200 applies electrical energy to the cell 100(e.g. to the first electrode 111). The fluid management system 400supplies liquid to the cell 100. The electrical energy applied to thecell 100 in turn heats to the liquid provided to the cell 100 so thatthe cell 100 outputs a heated fluid. This heated fluid is received bythe heat management system 300 and/or power management system 200, whichextract useable work (e.g. for heating and/or power generation) from theheated fluid. Once this work has been extracted, any power generated bythe power generation system 500 is provided to the power managementsystem 200. The used fluid is provided to the fluid management, whichprocesses this used fluid. This process may be repeated, e.g.continually, to provide heat and/or power generation.

A more specific example of a heat and power generating system 1000 willnow be described with reference to FIG. 5 .

FIG. 5 shows a heat and power generating system 1000. The heat and powergenerating system 1000 comprises a cell 100. Also included is a powersupply 30, a pump 18, and a drain 15. The system 1000 includes aplurality of heat exchangers, which, as shown in FIG. 5 includes a firstheat exchanger 301, a second heat exchanger 302, a third heat exchanger303 and a fourth heat exchanger 304. The system 1000 further includes aheat engine 510 having a first driving region 511 and a second drivingregion 512, and a generator 520. The cell 100 may comprise a plasma cell(e.g. a plasma-generating fuel cell).

The cell 100 is connected to receive two inputs (liquid and electricity)and to provide an output (heated fluid). The inputs to the cell 100 areshown at the bottom and right of the cell 100, and the output is at thetop.

The output of the cell 100 is coupled to each of the first heatexchanger 301 and the heat engine 510. A flow path for the output maysplit into two, with one path coupling to the first heat exchanger 301and another path coupling to the heat engine 510. In particular, theoutput from the cell 100 is coupled to the first driving region 511 ofthe heat engine 510. The heat engine 510 has a first engine inlet forreceiving fluid to drive the engine 510 in the first driving region 511.The first driving region 511 is also coupled to a first engine outletfor outputting the fluid which has driven the engine 510 in the firstdriving region 511. The first engine outlet is also coupled to the firstheat exchanger 301.

The engine 510 also includes a second engine inlet and a second engineoutlet. The second engine inlet is for receiving fluid to drive theengine 510 in the second driving region 512. The second engine outlet isfor outputting the fluid which has driven the engine 510 in the seconddriving region 512. The second engine inlet is also coupled to the firstheat exchanger 301. For example, fluid may flow from the first engineoutlet to the second engine inlet through the first heat exchanger 301.The engine 510 is coupled to a generator. Each of the first and seconddriving regions 511, 512 of the engine 510 may couple to the generator.The first and second driving regions 511, 512 may drive the engine 510at a different ratio. Both may contribute to driving the generator, andthus generating electricity.

The first heat exchanger 301 may be coupled to the second heat exchanger302. The system 1000 may be configured for heated fluid from the cell100 to flow through the first heat exchanger 301 and onto the secondheat exchanger 302. The second heat exchanger 302 may also be coupled tothe third and/or fourth heat exchangers 303, 304.

The power supply 30 is coupled to the cell 100. The power supply 30provides an input to the fuel supply (e.g. to provide electrical energyto the electrodes of the cell 100). The power supply 30 may include acoupling for receiving power from the mains (e.g. the power supply 30may receive three phase power). The power supply 30 may include aconverter (e.g. AC to DC) for providing DC output, such as a highvoltage DC output. The high voltage DC output may then be supplied tothe cell 100, e.g. to be applied to the first electrode 111. The powersupply 30 may also be coupled to the generator to receive generatedelectricity therefrom. The power supply 30 may receive AC or DC from thegenerator. Where AC is received, this may be converted to DC (e.g. usingthe same or a different AC to DC converter). Some of the electricitygenerated by the generator may be provided to the mains, e.g. for useelsewhere.

The third heat exchanger 303 and/or the pump 18 may couple to the inputfor the cell 100. Liquid to be supplied to the cell 100 may be heatedand/or pressurised using the third heat exchanger 303 and/or the pump18. This may provide the liquid input to the cell 100 which is used forgenerating heated fluid. The heated fluid output from the cell 100 isultimately coupled to a drain 15. For example, the fluid which haspassed through both regions 511, 512 of the engine 510 may be providedto the drain 15. Likewise, fluid which has passed through any of theheat exchangers (e.g. the second, third and/or fourth heat exchanger302, 303, 304) may then be coupled to the drain 15.

The system 1000 is arranged to provide multiple uses for the heatedfluid generated by the cell 100, e.g. to extract work from the heatedfluid in multiple ways. The system 1000 is configured to provide hightemperature, high pressure fluid output from the cell 100 to drive thefirst driving region 511 of the engine 510. The generator is configuredto generate electricity from this driving of the first driving region511. The first heat exchanger 301 is configured to reheat this fluidwhich has driven the first driving region 511 of the engine 510. Thefirst heat exchanger 301 is arranged to exchange heat between the heatedfluid from the cell 100 and the fluid which has driven the first drivingregion 511 of the engine 510. The system 1000 is configured to use there-heated fluid which has driven the first driving region 511 of theengine 510 to drive the second driving region 512 of the engine 510. Thesecond driving region 512 of the engine 510 is configured to have aneasier ratio (e.g. so that less energy is required to drive a rotation)as compared to the first driving region 511. The fluid passing throughthe second driving region 512 may be at a lower pressure than the firstdriving region 511. The generator is configured to generate electricityin response to driving of the first and/or second driving regions 511,512 of the engine 510.

The system 1000 is arranged for heated fluid which has passed throughthe first heat exchanger 301 and/or out the second engine outlet toprovide further heating use, where relevant. For example, the system1000 may be arranged to deliver the heated fluid to one or more of thesecond, third and/or fourth heat exchangers 302, 303, 304 for extractinguseable heating work from this heated fluid. Any of these heatexchangers 302, 303, 304 may couple to an external component for usingsuch heat. The system 1000 may be configured to exchange heat from theheated fluid with the liquid to be supplied to the cell 100 to provideheating thereof prior to being delivered to the cell 100. The system1000 is arranged to discard any remaining fluid using the drain 15.

In operation, liquid is supplied to the cell 100, and electrical energyis applied to the electrodes of the cell 100 to generate a heated fluid.The heated fluid leaves the cell 100 and flows to both the first heatexchanger 301 and the first driving region 511 of the engine 510. Theheated fluid flows through the first driving region 511 to drive theengine 510 and generator to generate electricity. This fluid then flowsinto the first heat exchanger 301 where it is re-heated by the heatedfluid which travelled directly (e.g. not via the engine 510) to thefirst heat exchanger 301 from the cell 100. The fluid that has travelledthrough the engine 510 is then reheated before flowing through thesecond engine driving region. This fluid then drives the engine 510 andgenerator to generate electricity. Fluid which has passed through thesecond driving region 512 of the engine 510 and/or through the firstheat exchanger 301 away from the engine 510 is then used in further heatexchangers 302, 303, 304 to extract more useable heat work from thefluid. This fluid is then discarded using the drain 15.

It will be appreciated in the context of the present disclosure that theexamples described herein are not intended to be considered limiting.Alternative and/or additional features may also be included. Forexample, reference has been made to concentric electrodes, e.g. whichare arranged coaxially with a central first electrode 111 and a secondelectrode 112 located radially outward form the first electrode 111.However, this arrangement may be reversed. Alternatively, the electrodesneed not be arranged concentrically. For example, the two electrodescould be arranged in an alternative fashion, such as being arranged asplate electrodes, e.g. two parallel plates, or as parallel wires orother parallel objections such as spheres.

Reference has been made herein to electrodes of the cell 100. The firstelectrode 111 may provide an anode, the second electrode 112 a cathode,and/or the third electrode 113 a balancing electrode. It is to beappreciated in the context of the present disclosure that each electrodemay provide a conductive path, e.g. each electrode may comprise aconductor extending along a length of the electrode. The anode maycomprise a conductor which provides a conductive path from external tothe internal portion 125 into the internal portion 125 to the distal endof the conductor within the internal portion 125. The cathode maycomprise a conductor which provides a conductive path from in, oradjacent to, the internal portion 125 to away from the internal portion125. The balancing electrode may comprise a conductor which provides aconductive path into the internal portion 125 from external to theinternal portion 125 or away from the internal portion 125 from withinthe internal portion 125. The first electrode 111 may be arranged topass closer to the third electrode 113 than it does to the secondelectrode 112, e.g. the minimum distance between a point on the firstelectrode 111 and a point on the third electrode 113 may be less thanthat for the first and second electrode 112. For example, the minimumdistance between first and third electrodes may be much less than thatfor the first and second electrodes 111, 112.

Examples described herein relate to use of one cell. However, it is tobe appreciated in the context of the present disclosure that multiplecells may be provided. For example, operation of the different cells maybe timed to provide a consistent output of heated fluid over time.Operational timing of each cell may be offset so that the total outputof heated fluid over time remains relatively constant. For example, itis to be appreciated that each cell may have an output of heated fluidwhich varies over time, and the multiple cells may have their operationstimed so that the output from all of the cells combined is moreconsistent than for the output of any one cell on its own. Thecontroller 40 may be configured to control the supply of liquid to eachcell, and/or the application of electrical energy to the electrodes toprovide consistent output of heated fluid. For example, one or moresensors may be used for each cell to determine operational parametersthereof, such as its output of heated fluid.

It is to be appreciated that the supply of liquid to the cell 100 mayhappen continuously over time or only in discrete time periods. Thecontroller 40 may be configured to control whether or not liquid isdelivered to the cell 100. For example, the cell 100 may comprise afluid inlet valve operable to control whether fluid can flow into theinternal portion 125 or not, and/or operation of the pump 18 may becontrolled to either deliver liquid to the cell 100 or not. There may bea continuous turnover of fluid within the cell 100, e.g. fluid iscontinually being provided to the cell 100 and heated fluid iscontinuously leaving the cell 100 (e.g. as a gas through the fluidoutlet 22). There may be discrete time periods for fluid input so thatone unit of liquid is delivered to the cell 100 (e.g. enough to fill thecell 100), then no further liquid is provided while electrical energy isapplied to the electrodes to provide heated fluid, e.g. once all thefluid has been heated sufficiently for release through the fluid outlet22. Then, another unit of liquid may be provided to the cell 100. It isto be appreciated that for this mode of operation, multiple differentcells being operated together may comprise timing operation so thatwhile unit is being delivered to one cell, another cell is applyingelectrical energy to the fluid in its cell. It will be appreciated thatmultiple different cells (e.g. more than 2) may be used with timings alloffset from each other, e.g. so that when one is nearly finishingheating, another is mid-heating, and another is just starting heatingetc.

The internal surface of the housing 120 has been described as being anelectromagnetic energy-absorbing surface. This may be a property of thematerial used to provide the housing 120, e.g. steel, and/or a coatingmay be provided on the internal surface to facilitate absorption ofelectromagnetic energy (e.g. from photon emissions). It is to beappreciated that absorbing electromagnetic energy may comprise receivingincident photons (e.g. in the visible light spectrum) and in response tosaid photons being incident on the surface, generating heat. It willalso be appreciated that electrons or other particles (e.g. chargedparticles emitted from the plasma/plasma-cooling process) may also beincident on the internal surface of the housing 120. The internalsurface of the housing 120 may also be configured to generate heat inresponse to such incident particles. For example, resistive heating maybe provided in response to electron flow through the internal surface.

It will be appreciated from the discussion above that the examples shownin the figures are merely exemplary, and include features which may begeneralised, removed or replaced as described herein and as set out inthe claims. With reference to the drawings in general, it will beappreciated that schematic functional block diagrams are used toindicate functionality of systems and apparatus described herein. Inaddition the processing functionality may also be provided by deviceswhich are supported by an electronic device. It will be appreciatedhowever that the functionality need not be divided in this way, andshould not be taken to imply any particular structure of hardware otherthan that described and claimed below. The function of one or more ofthe elements shown in the drawings may be further subdivided, and/ordistributed throughout apparatus of the disclosure. In some examples thefunction of one or more elements shown in the drawings may be integratedinto a single functional unit.

As will be appreciated by the skilled reader in the context of thepresent disclosure, each of the examples described herein may beimplemented in a variety of different ways. Any feature of any aspectsof the disclosure may be combined with any of the other aspects of thedisclosure. For example method aspects may be combined with apparatusaspects, and features described with reference to the operation ofparticular elements of apparatus may be provided in methods which do notuse those particular types of apparatus. In addition, each of thefeatures of each of the examples is intended to be separable from thefeatures which it is described in combination with, unless it isexpressly stated that some other feature is essential to its operation.Each of these separable features may of course be combined with any ofthe other features of the examples in which it is described, or with anyof the other features or combination of features of any of the otherexamples described herein. Furthermore, equivalents and modificationsnot described above may also be employed without departing from theinvention.

Certain features of the methods described herein may be implemented inhardware, and one or more functions of the apparatus may be implementedin method steps. It will also be appreciated in the context of thepresent disclosure that the methods described herein need not beperformed in the order in which they are described, nor necessarily inthe order in which they are depicted in the drawings. Accordingly,aspects of the disclosure which are described with reference to productsor apparatus are also intended to be implemented as methods and viceversa. The methods described herein may be implemented in computerprograms, or in hardware or in any combination thereof. Computerprograms include software, middleware, firmware, and any combinationthereof. Such programs may be provided as signals or network messagesand may be recorded on computer readable media such as tangible computerreadable media which may store the computer programs in non-transitoryform. Hardware includes computers, handheld devices, programmableprocessors, general purpose processors, application specific integratedcircuits (ASICs), field programmable gate arrays (FPGAs), and arrays oflogic gates. For example, any controller 40 described herein may beprovided by any control apparatus such as a general purpose processorconfigured with a computer program product configured to program theprocessor to operate according to any one of the methods describedherein. The functionality of the controller 40 may be provided by anapplication specific integrated circuit, ASIC, or by a fieldprogrammable gate array, FPGA, or by a configuration of logic gates, orby any other control apparatus.

Other examples and variations of the disclosure will be apparent to theskilled addressee in the context of the present disclosure.

1. A heating system comprising: a liquid supply system; a cellconfigured to: receive liquid from the liquid supply system, provideheating thereof, and output heated fluid; a work extraction systemconfigured to extract useable work from heated fluid output from thecell; wherein the cell comprises: (i) a housing arranged to define aninternal portion for receiving liquid to be heated, and (ii) a pluralityof electrodes configured to apply electrical energy to fluid in theinternal portion; and wherein the electrodes are configured to applyelectrical energy to said fluid in the internal portion to generate oneor more bubbles of plasma for releasing energy into said fluid in theinternal portion and the housing to provide heating of the fluid in theinternal portion.
 2. The heating system of claim 1, wherein the systemfurther comprises a controller configured to: (i) receive a signalindicative of at least one operational parameter of the cell, and (ii)control operation of the heating system based on said operationalparameter.
 3. The heating system of claim 2, wherein the controller isconfigured to control operation of the heating system so that heatand/or plasma generation in the cell is above a threshold level.
 4. Theheating system of claim 2, wherein controlling operation of the heatingsystem comprises controlling at least one of: (i) the supply of liquidto the cell by the liquid supply system, and (ii) the electrical energyapplied by the electrodes.
 5. The heating system of claim 4, wherein thecontroller is configured to control the supply of liquid to the celland/or the electrical energy applied by the electrodes based on anobtained indication of demand for heating to be provided by the cell. 6.(canceled)
 7. The heating system of claim 2, wherein the signalindicative of at least one operational parameter comprises an indicationof a quality and/or quantity of plasma generation within the cell; andwherein the controller is configured to control operation of the heatingsystem so that the quality and/or quantity of plasma generation remainswithin a selected range.
 8. (canceled)
 9. The heating system of claim 2,wherein the controller is configured to control at least one of: (i) thesupply of liquid to the cell based on the electrical energy to beapplied by the plurality of electrodes, and (ii) the electrical energyto be applied by the plurality of electrodes based on the supply ofliquid to the cell.
 10. The heating system of claim 2, wherein thesignal indicative of at least one operational parameter comprises anindication of a temperature associated with at least one of: the cell,the fluid in the cell, and the fluid output from the cell; and whereinthe controller is configured to control at least one of: (i) theelectrical energy applied by the electrodes, (ii) the supply of liquidto the cell, and (iii) an external heater, to increase the temperatureof the cell, the fluid in the cell, and/or the fluid output from thecell in the event that the indication of temperature is below athreshold level.
 11. The heating system of claim 10, wherein thecontroller is configured to increase the electrical energy applied bythe electrodes to provide increased heating and/or decrease the flowrate of liquid through the cell in the event that the indication oftemperature is below the threshold level.
 12. The heating system ofclaim 1, wherein an internal surface of the housing of the cellcomprises an electromagnetic energy-absorbing material arranged toconvert incident photons into heat.
 13. The heating system of claim 1,wherein the liquid supply system is configured to supply liquid to thecell under pressure, and the cell is arranged to retain fluid in thehousing under pressure.
 14. The heating system of claim 1, wherein theliquid supply system is configured to increase heating of liquid priorto supplying it to the cell in the event that heat and/or plasmageneration of the cell is below a threshold level.
 15. The heatingsystem of claim 1, wherein the plurality of electrodes comprises: (i) ananode arranged to provide a conductive path for current to be applied tofluid in the internal portion, and (ii) a cathode arranged to provide aconductive path away from the internal portion for current received fromthe anode through the fluid in the internal portion.
 16. The heatingsystem of claim 15 further comprising a balancing electrode arranged toprovide an additional conductive path towards or away from fluid in theinternal portion, for example wherein the anode, cathode and balancingelectrode all have the same coefficient of thermal expansion.
 17. Theheating system of claim 16, wherein the balancing electrode is separatedfrom the conductive path from the first electrode to the secondelectrode, for example wherein the balancing electrode extendsperpendicularly away from the conductive path from the first electrodeto the second electrode, for example wherein the balancing electrode isarranged to be closer to the first electrode than the second electrodeis.
 18. The heating system of claim 15, wherein the cell comprises aresistive element arranged between the anode and cathode, for examplewherein the resistive element comprises quartz.
 19. The heating systemof claim 15, wherein the anode and cathode are arranged concentricallywith each other.
 20. (canceled)
 21. (canceled)
 22. (canceled)
 23. Amethod of providing a heated fluid for extracting useable worktherefrom, the method comprising: supplying a liquid to be heated to acell, wherein the cell comprises: (i) a housing arranged to define aninternal portion for receiving the liquid to be heated, and (ii) aplurality of electrodes configured to apply electrical energy to fluidin the internal portion; controlling operation of the plurality ofelectrodes to apply electrical energy to fluid in the internal portionto generate one or more bubbles of plasma; generating heat in thehousing proximal to the internal portion in response to the housingreceiving incident photons associated with plasma bubbles in theinternal portion; using the housing to conductively heat fluid in theinternal portion.
 24. A method of controlling operation of a heatingsystem, the heating system comprising a cell comprising: (i) a housingarranged to define an internal portion for receiving liquid to beheated, and (ii) a plurality of electrodes configured to applyelectrical energy to fluid in the internal portion, the methodcomprising: controlling operation of the electrodes to apply electricalenergy to fluid in the internal portion to generate one or more bubblesof plasma for releasing energy from the plasma into the fluid in theinternal portion and the housing to provide heating of the fluid in theinternal portion, wherein controlling operation of the electrodescomprises: receiving a signal indicative of at least one operationalparameter associated with the cell and/or a fluid associated therewith;operating in a ‘cold-start’ mode when the operational parameterindicates heating and/or plasma generation is below a threshold level;and operating in a ‘normal’ mode when the operational parameterindicates heating and/or plasma generation is above the threshold level;wherein operating in the cold-start mode comprises controlling at leastone of: (i) the electrical energy applied by the electrodes, (ii) supplyof liquid to the cell, and (iii) operation of an external heater, toincrease the temperature of the cell and/or the fluid associatedtherewith in the event that the operational parameter indicates heatingand/or plasma generation is below a threshold level.
 25. A computerprogram product comprising computer program instructions configured tocontrol a processor to perform the method of claim 23.